The present invention relates generally to security tags for use with an electronic security system for detecting the unauthorized removal of articles and, more particularly, to such security tags which are activatable and deactivatable.
The use of electronic article security systems for detecting and preventing theft of articles or goods from retail establishments and/or other facilities, such as libraries, has become relatively widespread. In general, such security systems employ a label or security tag which is affixed to, associated with, or otherwise secured to an article or item which is readily available to potential customers or facility users and therefore may be easily removed. Security tags may take on many different sizes, shapes and forms, depending upon the particular type of security system in use, the type and size of the article, etc. In general, such security systems are employed for detecting the presence or the absence of the security tag and thus a protected article generally as the protected article passes through or near a particular protected or security area. In most cases, the protected area is located at or around an exit or entrance to the retail establishment or other facility.
One such electronic article security system which has gained popularity utilizes a security tag which includes a self-contained, operatively tuned or resonant circuit in the form of a small, generally planar tag which resonates at a known predetermined detection frequency. A transmitter, which is also tuned to the particular detection frequency, is employed for transmitting electromagnetic energy into the protected or security area. A receiver, also tuned to the detection frequency, is positioned generally proximate to the protected area. Typically, the transmitter is located on one side of an exit and the receiver is located on the other side of the exit. In this manner, when an article having an attached security tag moves into or otherwise passes through the protected area, generally just before passing through the exit, the tag is exposed to the transmitted energy. Upon receiving the transmitted energy, the resonant circuit within the tag resonates, thereby providing an output signal detectable by the receiver. When the receiver detects such an output signal, indicative of the presence of an article with a security tag within the protected area, the receiver activates an alarm to alert appropriate security personnel.
While such systems are generally effective in deterring theft, there is a need to prevent the accidental activation of such security systems by a person who has actually purchased an article and, after paying for the article, is leaving the store or other facility. It is generally impractical to deactivate the entire security system so, in most cases, the security tag is, itself, deactivated. One method of deactivating the security tag is to physically remove the tag from the purchased article. However, removal of the tag, which is generally secured to an article in a manner designed to prevent removal by a would-be thief, can be difficult and time-consuming and requires, in some cases, additional removal equipment and/or specialized training. A second method of deactivating the security tag is to cover the security tag with a special shielding device, such as metallized sticker, to prevent the transmitted energy from reaching the resonant circuit. Again, while such stick-on shielding devices can be effective, they require additional time and effort at the checkout counter and permit thieves to identify an easy way in which to defeat the security system.
A more recent and generally more effective tag deactivation technique involves either short-circuiting the resonant circuit or creating an open circuit to completely prevent the circuit from resonating. Deactivatable tags of this type are disclosed in U.S. Pat. Nos. 4,498,076 entitled "Resonant Tag and Deactivator for Use in an Electronic Security System"; 4,728,938 entitled "Security Tag Deactivation System"; and 4,835,524 entitled "Deactivatable Security Tag," all of which are incorporated herein by reference.
Deactivatable tags of the type disclosed in the referenced patents have been shown to be effective and can be conveniently deactivated at a checkout counter by momentarily placing the tag above or near a deactivation device which subjects the tag to electromagnetic energy at a power level sufficient to cause the resonant circuit to either short or open, depending upon the structure of the tag. However, one drawback encountered with the use of such a tag deactivation system is that the tag must be maintained above or near the deactivation device for a time which is sufficient for complete deactivation. However, the person at the checkout counter generally has no way of knowing for sure that the security tag has been deactivated completely. As a result, when a customer leaves the retail facility with the article the tag may still resonate enough to activate the security system, particularly when the security system is very sensitive.
It is also desirable to have the ability to preplace a security tag, either on, within or upon the packaging of an article. Preplacing of a tag may be accomplished at the same time that the article is manufactured as a basic part of the manufacturing process or as part of the packaging or shipping process for the article. In this manner, as the article passes through its distribution chain, when it finally arrives at the retail level, the retail store need not go to the trouble and expense of adding a security tag to the article. One drawback of a preplaced tag is that the retail facility which markets the article to the public may or may not utilize an electronic security system. Since it is impractical for a manufacturer to be able to differentiate between products having a tag associated therewith and products having no tag associated, the manufacturers incorporate the tag into all products or packaging therefor. Hence, there is a need for a security tag which can be selectively activated by a retailer if the retailer utilizes an electronic security system and which will have no detrimental effect in the event that the retailer does not utilize an electronic security system.
The present invention overcomes many of the problems associated with the prior art by providing a security tag which is both activatable and deactivatable. The security tag, when received by a user, such as a retailer, is generally preapplied to an article or the packaging for the article and has a resonant circuit initially tuned to a first resonant frequency which is above or outside of the detection frequency range of the security system and thus is unusable. When it is desired to activate the tag for use, the tag is exposed to electromagnetic energy at the first frequency and with sufficient power to fuse and short-circuit a controlled portion of the tag, thereby changing the resonant frequency of the tag to a second resonant frequency which is within the detection frequency range of the security system. Proper activation of the security tag can be verified by exposing the tag to electromagnetic energy within the detection frequency range and confirming that the resonant circuit resonates. Once activated, the tag may be secured to an article in any known manner for security purposes. Alternatively, the security tag could be secured to the article prior to activation. If the tag is not activated, it will not interact with or otherwise affect or be affected by the electronic security system.
When a customer purchases the article, the security tag is deactivated by exposing the resonant circuit to electromagnetic energy at the detection frequency and with sufficient power to again fuse and short-circuit a controlled portion of the security tag. The short-circuiting of the second portion of the security tag changes the resonant frequency of the tag to a third frequency within a third frequency range which is also outside of the detection frequency range. Proper deactivation of the security tag may be conveniently verified by exposing the resonant circuit to electromagnetic energy within the third frequency range and determining whether the resonant circuit resonates. If the resonant circuit resonates at the third frequency, it is precluded from resonating at the detection frequency and, therefore, the security tag will not accidentally trigger a security system as the purchaser leaves the retail store facility with the purchased article.